[en] Objective: To study the radiological features and biomechanics of stress fracture. Methods: The X-ray, CT, MRI, and ECT signs in 20 cases of stress fracture and its correlation to biomechanics were analyzed. Results: Of the 20 cases, 14 cases occurred in the tibia, 2 cases in the metatarsal bone, 1 case in the rib, 1 case in the neck of femur and ribs, 1 case in the middle-inferior part of the femur, and 1 case in the fibula. Tow early cases of stress fracture demonstrated a characteristic sign of 'gray cortex'. The spherical or abnormal generation of bony callus and periosteum proliferation that demonstrated 'double cortex' sign in 2 cases were the sign of bone remodeling and the 'button sign' was the sign of bone healing. CT scan could clearly show the pathologic changes of bone and the soft tissue edema. Bone callus showed low signal on T₁WI and slight high signal on T₂WI. The area of bone edema on MRI that demonstrated low signal on T₁WI and high signal on T₂WI was larger than that on CT. MRI showed a linear band of low signal on both T₁WI and T₂WI in the area of bone fracture. ECT showed a focal area of increased uptake in the abnormal areas. The areas of bone stress fracture were characteristic and accorded with the biomechanical weak area in the bone. Conclusion: Stress fracture occurs in the special parts of the bone and has characteristic imaging features. X-ray should still be used to find the fracture of bones in the first inspection. CT and MRI are very helpful in the differentiation. Although sensitive, bone scan has lower specificity than either CT or MRI. (authors)

[en] Objective: To investigate the applicative value of multi-slice CT (MSCT) perfusion imaging on quantitative assessment of tumor angiogenesis before and after interventional therapy and monitoring the early interventional therapeutic effect in malignant soft-tissue tumor. Methods: Twenty-four New Zealand white rabbits successfully implanted VX₂ tumor in the unilateral proximal thigh were divided into two groups (twelve per group) at random and performed conventional CT plain scan and perfusion scan 14 days after implantation and 3 days after interventional therapy respectively. The values of blood flow (BF), blood valume (BV), mean transit time (MTT) and premeability surface (PS) of VX₂ tumors and normal muscular tissues were computed and the differences among them were analyzed. Meanwhile, correlative analysis between perfusion parameters and micro-vessel density(MVD) counts, average A value of vascular endothelial growth factor(VEGF) was done. Results: Before interventional therapy, the values of BF, BV, MTT and PS of VX₂ tumors in interventional group were (303.3 ± 69.9) ml· 100 g^-1·min^-1, (7.02 ± 3.10) ml/100 g, (1.99 ± 0.28) s and (65.9 ± 9.4) ml·100 g^-1·min^-1 respectively. Compared with the parametric values of normal muscular tissues, there were significant differences between them (F value was 4285.82, 1867.46, 413.04 and 698.42 respectively, P<0.01). There were no significant differences of the above parametric values between interventional group and the control group (F value was 2.47, 2.03, 0.02 and 0.53 respectively, P>0.05). The values of MVD counts, average A value of VEGF of VX₂ tumors in interventional group were 50.1 ± 4.1/HP and 0.352±0.011 respectively. There were no significant differences between interventional group and the control group (F value was 0.02 and 0.19 respectively, P>0.05). Three days after interventional therapy, the values of BF, BV, MTT, PS, MVD and VEGF of VX₂ tumors in interventional group were (7.5 ± 2.4) ml· 100 g^-1·min^-1, (1.20 ±0.23) ml/100 g, (3.29 ± 0.57) s, (4.0 ± 1.5) ml·100 g^-1·min^-1, 16.0 ± 2.4/HP and 0.215 ± 0.008 respectively. Compared with the values of pre-interventional therapy and the control group, there were significant differences among them (P<0.01). Additionally, the values of BF, BV, PS in VX₂ tumors had a significant positive correlation with MVD counts, average A value of VEGF (r>0.7, P<0.05), however, the value of MTT had no significant correlation with MVD (P>0.05) but had a significant negative correlation with average A value of VEGF (r=-0.78, P<0.05). Conclusion: MSCT perfusion imaging is a functional imaging technique that is capable of quantitative assessment to tumor angiogenesis, blood perfusion and vascular permeability, which can evaluate the early interventional therapeutic effect in malignant soft-tissue tumor invasively and accurately. (authors)

[en] Objective: To study the MRI volume of the amygdala and hippocampus in patients with major depression. Methods: Quantitative MRI of the amygdala and hippocampus was studied in 22 patients with major depression and compared with 13 age-matched controls. Results: Both groups exhibited similar significant hippocampal asymmetry (left smaller than right). The volume of the bilateral hippocampus was significantly smaller in the patient group than that in the controls (left: t=9.96, P<0.01; right: t=11.88, P<0.01). The right amygdala was smaller in the patient group than that in the control group (t=5.50, P<0.01), No correlation was found between the hippocampal volume abnormalities and the course of disease. Conclusion: These findings support the hypothesis that the hippocampus and amygdala within limbic-cortical networks may play a crucial role in the pathogenesis of major depression. (authors)

[en] A single Cr-rich σ-phase alloy with a composition of Co₁₇Cr₄₆Fe_16.3Mn_15.2Ni_5.5 (at.%) and a tetragonal lattice structure was produced. The tracer diffusion coefficients of Ni and Fe were measured by secondary ion mass spectroscopy using the highly enriched ⁶⁴Ni and ⁵⁸Fe natural isotopes. On the homologous temperature scale, Ni and Fe diffuse in the σ phase faster as compared to the corresponding diffusion rates in the equiatomic and face-centered cubic CoCrFeMnNi alloy. In contrast, on the absolute temperature scale, these elements diffuse roughly at the same rates in both materials. Factors influencing element diffusion and phase stability of the σ phase compared to the equiatomic alloy are discussed.

[en] Lithium ions are widely used in many scientific fields; in order to get these ions, it is necessary to study lithium plasma process thoroughly. Recently, a hybrid ${}^7$Li${}^{3+}$ ion source has been designed and tested at Peking University (PKU). To understand the lithium plasma behaviour inside the plasma chamber and to provide some guidelines for ion source optimization to generate ${}^7$Li${}^{3+}$, a numerical model based on the plasma equilibrium equations is developed in this work, which is helpful not only for our ion source, but also for understanding the physical process of lithium plasma from ECR ion sources with different frequencies. This model can describe the density and fraction of lithium ions in various system parameters. The dependences of the Li${}^{+}$, Li${}^{2+}$, and Li${}^{3+}$ ion density and fraction on electron temperature, gas pressure, microwave power, surface ionizer, and the magnetic field are investigated systematically. (© 2021 Wiley‐VCH GmbH)

[en] Acrylonitrile-Butadiene Rubber (NBR) is one of the widely used synthetic rubbers currently used for a variety of non-tire rubber products. Ion implantation is foreseen to be an efficient way to improve the NBR surface characteristic such as lower coefficient, higher resistance. Ion implantation with N⁺ and H⁺ ions was carried out to treat NBR surface to understand the irradiation influence on functional properties of the vulcanizates, like friction and hardness on Peking University (PKU) ion source test bench recently. Analysis on friction coefficient, hardness. thermal aging resistance, tribology and wear resistance were done after ion implantation. (authors)

[en] The current study aimed to explore the moderating role of psychological resilience in the association between workload and depressive symptoms among radiology residents during standardized residency training (SRT) in China. A nationwide cross-sectional online survey was conducted among radiology residents in China. Workload was measured by working hours per week and the frequency of frontline nightwork in the last month. Resilience was assessed by the 2-item Connor-Davidson Resilience Scale. Depressive symptoms were measured by the Depression Anxiety Stress Scales. The hierarchical regression and simple slope analyses were performed to examine the moderating effect of resilience. Among 3666 radiology residents, the mean age was 27.3 years (SD = 2.6) and 58% were female. About 24.4% of the participants reported medium to severe depressive symptoms. The hierarchical regression showed that working hours (b${}_a$ = 0.11, 95%CI: 0.08, 0.14) and having frontline nightwork more than once (b${}_a$ = 1.22, 95%CI: 0.67, 1.78) were positively associated with depressive symptoms; the moderating effect of resilience was significant in the association of depressive symptoms with working hours (b${}_a$ = - 0.02, 95%CI: - 0.03, - 0.01) and having frontline nightwork more than once (b${}_a$ = - 0.28, 95%CI: - 0.49, - 0.07). The simple slope test showed the association between workload-related variables and depressive symptoms was only significant in those with a relatively lower level of resilience. The study found that resilience was an important modifier buffering the positive association between workload and depressive symptoms among radiology residents in China. Future medical training programs are suggested to include effective intervention components to increase personal resilience. Heavy workload in clinical setting may pose adverse effect on mental health and job performance of radiology residents. The study investigated whether psychological resilience would mitigate the association between workload and depressive symptoms among Chinese radiology residents.

[en] Objective: To investigate the therapeutic effect of hypoxia inducible factor-1 α (HIF-1 α) combined with transcatheter arterial embolization (TAE) on rabbit VX2 liver tumor model. Methods: Twenty-four VX2 liver cancer model rabbits were randomly divided into 4 groups of 6 each. On the 14th day of VX2 tumor implantation, 3 rabbits were randomly selected and executed in each group, and the remaining 3 rabbits underwent interventional therapy on the same day. In group A, the PVA particles and contrast agent suspension were injected into the hepatic artery. In group B, the HIF-1 α-shRNA solution was injected into the hepatic artery. In group C, the PVA particles and contrast medium suspension as well as HIF-1 α-shRNA solution were injected into the hepatic artery. In group D as control group, the hepatic artery was injected with normal saline. The rabbits in each group were killed on the 14th day after interventional therapy. The expression levels of mRNA and protein were detected using the real-time reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry assays. Results: The Hand E staining showed mitotic figures of 11.33 ± 3.51 in the TAE group, 13.42 ± 3.96 in the HIF-1 α-shRNA group, 7.33 ± 2.31 in the TAE + HIF-1 α-shRNA group and 20.50 ± 4.18 in the control group. Compared with the control, TAE, and HIF-1 α-shRNA groups, the TAE + HIF-1 α-shRNA group significantly inhibited the protein expression of HIF-1 α and VEGF (PHIF-1 α < 0.001; PVEGF < 0.001). The immunohistochemical staining and RT-PCR assay showed that the expression levels of HIF-1 α and VEGF in TAE + HIF-1 α-shRNA group were both significantly lower than those in other groups (P < 0.001). Conclusion: HIF-1 α-shRNA improves therapeutic effect of TAE by inhibiting expressions of HIF-1 α and VEGF on rabbit VX2 liver tumor model. (authors)